tbuckley/cabot-search huggingface dataset:
IMMU-21. LOW-INTENSITY PULSED ULTRASOUND PROMOTES THE PRESENTATION OF BRAIN-DERIVED ANTIGENS THROUGH ENHANCED TRAFFICKING OF ANTIGEN-PRESENTING CELLS FROM THE BRAIN INTO THE PERIPHERY
Authors: Marco Gallus, Victor Arrieta, Atsuro Saijo, Jeffrey Haegelin, Pavlina Chuntova, Akane Yamamichi, Li Chen, Karl Habashy, Andrew Gould, Christina Amidei, Catalina Lee Chang, Roger Stupp, Michael Canney, Adam Sonabend, Hideho Okada
Journal: Neuro-Oncology (2023)

Abstract The central nervous system, immunologically unique due to specialized lymphatics and anatomical barriers, often conceals brain neoplasm from the peripheral immune system. Low-intensity pulsed ultrasound with microbubbles (LIPU/MB) enables transient opening of the BBB, allowing drug transport and immune cell trafficking into brain tumors. However, it remains unclear whether BBB opening promotes immune cell trafficking from the brain to the periphery. To investigate this, we performed intravital imaging of Colony-stimulating factor receptor 1 (CSFR1) and CX3CR1 reporter mice to visualize antigen-presenting cell locomotion in the brain before and immediately after LIPU/MB using two-photon microscopy. Within one hour after LIPU/MB, we observed the exiting of CSFR1+ and CX3CR1+ immune cells from the brain parenchyma and perivascular space into the bloodstream, a phenomenon we did not observe prior to LIPU/MB treatment. To further evaluate the immunological effects of LIPU/MB on brain antigen presentation, we performed LIPU/MB in novel transgenic mice that express a minigene encoding for 4 immunogenic peptides under the glial fibrillary acidic protein (GFAP) promotor. We observed significant proliferation of naïve antigen-specific CD8 T cells targeting one of the peptides in the cervical lymph nodes one week after LIPU/MB treatment, but not in the animals that received T cells but did not undergo LIPU/MB. These data indicate that LIPU/MB facilitates the presentation of brain-localized antigens to antigen-reactive T cells in the systemic circulation. In 3 out of 5 GBM patients that underwent LIPU/MB plus doxorubicin and anti-PD-1 blocking antibodies, we observed CD11b+CD14+P2YR12+ microglia in blood samples collected after sonication. This increase was present in cycles 3-6 of this treatment. We did not observe the presence of this immune cell population in blood samples from healthy donors. Taken together, our results indicate that LIPU/MB could be a novel approach to enhance brain-antigen presentation in the periphery.
RTID-02. SILMET TRIAL: A RANDOMIZED, PLACEBO-CONTROLLED STUDY TO EVALUATE SILIBININ IN PREVENTING INTRACRANIAL RECURRENCE AFTER COMPLETE RESECTION OF A SINGLE BRAIN METASTASIS FROM NSCLC OR BREAST CANCER
Authors: Alessia Pellerino, Andrea Pace, Filippo Flavio Angileri, Maria Caffo, Marco Gatti, Alessandro Olivi, Quintino Giorgio D'Alessandris, Alessandra Fabi, Luca Bertero, Alessia Andrea Ricci, Luca Mangherini, Diego Garbossa, Neibla Priego, Joaquim Bosch-Barrera, Manuel Valiente, Riccardo Soffietti, Roberta Rudà
Journal: Neuro-Oncology (2023)

Abstract BACKGROUND: A subpopulation of reactive astrocytes (RAs) with activated signal transducer and activator of transcription 3 (STAT3) signalling in peritumoral tissue of brain metastases (BM) has been shown to favor a pro-metastatic microenvironment. High-pSTAT3 expression in RAs of BM has been correlated with a shorter intracranial progression-free survival (i-PFS) as compared with low-pSTAT3 BM. Pharmacological inhibition of the STAT3 pathway with silibinin has been suggested to be active in preliminary cohort of patients with BM. Patients and methods. A new “prevention” trial has been initiated in June 2023 to investigate the efficacy of silibinin in comparison to placebo (PCB) to prevent a secondary intracranial relapse in a multicentric cohort of patients with gross-total resected BM from NSCLC and breast cancer. Inclusion criteria are as follows: histologically confirmed BM from NSCLC or BC; single BM who underwent a complete resection; systemic disease not requiring a change of antineoplastic therapy; pSTAT3 presence in RAs of peritumoral tissue confirmed by central assessment; ≥ 18 – 70 years of age; KPS ≥ 70. The primary endpoint is to demonstrate a superiority of silibinin in prolonging time to local recurrence as compared to PCB. The secondary endpoints are time to distant recurrence of BM in the brain, i-PFS, overall PFS (intracranial and/or systemic), overall survival, tolerability, quality of life. Collection of blood and CSF samples for the analysis of STAT3 downstream pathways is an exploratory objective. The sample size (70 patients) was calculated by assuming a median time to local recurrence of BM of 7.5 months for PCB (control arm) according to Mahajan [1] and ≥15 months for silibinin arm. Clinical trial information: NCT05689619 [1] Mahajan A et al. Post-operative stereotactic radiosurgery versus observation for completely resected brain metastases: a single-centre, randomised, controlled, phase 3 trial. Lancet Oncol. 2017
IMMU-29. A CHIMERIC ONCOLYTIC ADENOVIRUS CIRCUMVENTS NEUTRALIZING ANTIBODIES DEVELOPED BY PATIENTS WITH RECURRENT GLIOBLASTOMA TREATED WITH DELTA-24-RGD
Authors: Dong Ho Shin, Hong Jiang, Andrew Gillard, Xuejun Fan, Sanjay Singh, Andres Lopez-Rivas, Jiasen He, Joy Gumin, Frederick Lang, Candelaria Gomez-Manzano, Juan Fueyo-Margareto
Journal: Neuro-Oncology (2023)

Abstract Oncolytic virotherapy holds great potential to treat high-grade gliomas by harnessing virus-mediated oncolysis to stimulate anti-tumor immune responses. However, the efficacy of oncolytic adenoviruses can be hampered by neutralizing antibodies. In this study, we examined sera obtained from a phase 1 clinical trial using oncolytic adenovirus Delta-24-RGD to treat patients with recurrent malignant gliomas. We found that a single intratumoral injection of Delta-24-RGD induced the development of neutralizing antibodies in less than half of the patients but demonstrated remarkable outcomes, with 20% of the patients surviving beyond three years. Conversely, multiple injections of the oncolytic adenovirus induced neutralizing antibodies in 80% of patients (P=0.05) but resulted in no long-term survivors. This inverse correlation led us to further investigate the role of neutralizing antibodies during glioma virotherapy. Examination of Delta-24-RGD-treated murine brain tumors using immunofluorescence displayed colocalization of antibodies and viral proteins. To counteract virus neutralization and maximize oncolysis, we engineered a chimeric virus, Delta-24-RGD-H43m, by replacing the hypervariable regions of the hexon protein from the prevalent serotype 5-based Delta-24-RGD with those from the rare serotype 43. The infectivity, replication, and oncolytic capabilities of Delta-24-RGD-H43m were similar to those of the parental virus. Using clinical trial patient sera, we observed that Delta-24-RGD-H43m displayed significant resilience against the inhibitory effects of neutralizing sera from patients (P=0.01). In murine models with pre-existing immunity to adenovirus, Delta-24-RGD-H43m treatment led to a significantly extended median survival and resulted in a higher percentage of long-term survivors than the parental virus (P=0.005). These results underscore the effectiveness of hexon swapping as a strategy to overcome the dominant immune response against oncolytic viruses, provide valuable insights into the interaction between oncolytic viruses and the host immune system, and lay the foundation to translate to the clinical setting immune-evading virotherapies for glioma patients.
NCMP-20. ASSESSING THE IMPACT OF DRIVER MUTATIONS AND ANTINEOPLASTIC TREATMENTS ON RISK FOR STROKE RECURRENCE IN PATIENTS WITH LUNG ADENOCARCINOMA
Authors: Sanghee Lim, Zafer Keser, Ivan Carabenciov, Ugur Sener
Journal: Neuro-Oncology (2023)

Abstract BACKGROUND Hypercoagulability is a well-described paraneoplastic phenomenon associated with strokes in cancer patients, but whether driver mutations or antineoplastic treatments contribute in a significant way to recurrent stroke risk are not well understood. METHODS As part of a larger study focusing on lung cancer and stroke, we retrospectively identified 103 patients with tissue-confirmed adenocarcinoma and prior diagnosis of stroke treated at the Mayo Clinic between 2000-2022. We collected data regarding demographics, performance status, cerebrovascular risk factors, antithrombotic use, chemotherapy, radiation, and genetic testing data, which were assessed for impact on recurrent stroke risk. RESULTS 71.8% of patients had recurrent strokes (74/103). No class of chemotherapeutics was significantly associated with increased risk for recurrent strokes, including immune checkpoint inhibitors and thrombogenic chemotherapeutics (Gemcitabine, Cisplatin, Carboplatin, anti-VEGF therapies). 78 patients had genetic testing data available. Driver mutations in KRAS, EGFR, MET, and BRAF were not associated with increased risk for recurrent stroke. There was a signal towards increased risk for stroke recurrence in patients with ALK mutations (OR 2.647, p=0.4056). There was a trend towards increased risk for stroke recurrence in patients with advanced staging (Stage III/IV) at diagnosis (OR 2.125, p=0.09). Stroke recurrence risk was higher in patients treated with single antiplatelet agents compared to anticoagulation or dual antiplatelet therapy (OR 3.385, p=0.0061) though risk of hemorrhagic complications was similar (OR 1.559, p=0.3376). Patients with recurrent stroke had longer overall survival compared to those without (Median OS 43.2 months vs 26.3 months, Mantel-Haenszel HR 0.5202, p=0.0367). CONCLUSIONS In patients with lung adenocarcinoma who experienced ischemic stroke, prolonged survival and single antiplatelet therapy compared to dual antiplatelet therapy or anticoagulation were associated with increased recurrent stroke risk. ALK mutations and higher stage at initial diagnosis trended towards higher risk for stroke recurrence. Larger retrospective analyses are under way to confirm these findings.
CCRG-01. INFERENCE OF CELL CYCLE REGULATION BETWEEN GLIOBLASTOMA SUBPOPULATIONS IN VIVO TO DRIVE COMPUTATIONAL AND MATHEMATICAL MODELS OF THE CANCER COMPLEX SYSTEM
Authors: Nicholas Harbour, Lee Curtin, Sebastian Velez, Michael Chappell, Matthew Hubbard, Osama Al-Dalahmah, Peter Canoll, Markus Owen, Kristin Swanson
Journal: Neuro-Oncology (2023)

Abstract Glioblastoma (GBM) is the most aggressive and most common primary malignant brain tumor in adults, with a poor median survival time of 15 months. One of the key challenges in treating GBM is its highly heterogeneous nature, with multiple distinct subtypes that have been shown to occur on both inter- and intra-patient levels. Three main classifications, known as classical/proliferative, mesenchymal and proneural have become commonly demonstrated phenotypes. The cell cycle is a fundamental and highly conserved process that controls faithful division of cells; dysregulation of the cell cycle is known to be a key driver in many cancers. However, how the cell cycle is differently regulated between these subtypes has not been well classified in vivo. We investigate these three GBM subtypes using a recently published single nucleus RNAseq (snRNAseq) data set. We compare cell cycle regulation/dysregulation among these three subtypes using Tricycle, an R/Bioconductor package that utilises dimension reduction via principal component analysis and transfer learning to infer cell cycle position from any snRNAseq data set. We find that the classical GBM subtype has the highest proportion of actively dividing cells (cells in: S/G2/M phases), while the mesenchymal and proneural subtypes have a very low proportion of actively dividing cells. This supports the idea of a proliferation-migration dichotomy between GBM subtypes. We use this proportion of actively proliferating cells to calibrate a minimal spatiotemporal mathematical model for GBM tumor growth that accounts for the differences in cell cycle regulation between these three GBM subtypes.
EPCO-28. MULTIPLATFORM MOLECULAR AND FUNCTIONAL GENOMIC ANALYSES OF <i>NF1</i> MUTANT GLIOBLASTOMA IDENTIFY DISTINCT CO-MUTATION PATTERNS AND DRUGGABLE DEPENDENCIES UNDERLYING SELUMETINIB RESPONSE
Authors: Kanish Mirchia, Emily Payne, Sixuan Pan, Nadeem Al-Adli, Jacob Young, William Chen, Joanna Pak, Kyounghee Seo, Tomoko Ozawa, Alyssa T Reddy, Arie Perry, John Liu, Mitchel Berger, David Raleigh, Harish Vasudevan
Journal: Neuro-Oncology (2023)

Abstract The tumor suppressor NF1 is recurrently mutated in sporadic IDH-wildtype glioblastoma and activates Ras/Raf/MEK signaling, motivating the use of targeted MEK inhibition. Here, we combine multiplatform molecular analysis of NF1 mutant glioblastoma human resection specimens with functional genomic CRISPRi screens to the MEK inhibitor selumetinib. METHODS: We identified 123 consecutive patients treated at the University of California San Francisco between 2016-2022 with NF1 mutant, IDH-wildtype glioblastoma. DNA methylation data was processed using the minfi package, and hierarchical clustering, principal component analysis (PCA), and survival analysis was performed in R. Human NF1 mutant GBM43 and mouse NRAS mutant SB28 GBM cells expressing CRISPRi machinery were used for genome wide selumetinib-resistance screens. Immunoblotting was performed to validate CRISPRi screen hits and selumetinib responses in cell lines. RESULTS: DNA sequencing of human glioblastomas identified 12 recurrent alterations in greater than 10% of cases including cell cycle regulators (CDKN2A/B, TP53, RB1), PI3K signaling (PTEN, PIK3R1, PIK3CA), epigenetic regulators (ATRX, SETD2), and Ras signaling (EGFR, PDGFRA, PTPN11). Methylation data (n=55 tumors) identified three groups marked by differences in MGMT methylation (p=0.04, chi-square test) and CDKN2A/B loss (p=0.01, chi-square test). CRISPRi screens in GBM43 and SB28 cells identified driver phenotypes in cell cycle regulators (TP53, CDKN2A, CDK4), PI3K signaling (PTEN, MTOR), and Ras signaling (RASA2, PTPN11) consistent with co-occurring mutations in the human NF1 mutant glioblastoma cohort. In contrast, mediators of selumetinib response converged on regulators of Ras/Raf/MEK signaling including the Ras effector SHOC2. Biochemical analysis validated SHOC2 repression is sufficient for selumetinib sensitization. CONCLUSIONS: Using a combination of human tumor genomic analysis, functional genetic screens, and biochemical validation, we identify three epigenetic groups of NF1 mutant glioblastoma with distinct co-mutation patterns and validate compensatory Ras/Raf/MEK activation as a conserved mechanism of selumetinib resistance, suggesting combination molecular therapy as a rational therapeutic combination.
BIOS-01. EFFICACY AMONG THERAPEUTICALLY EFFECTIVE ABSORBED DOSE PATIENTS IN RESPECT-GBM PHASE I OF RHENIUM-186 NANOLIPOSOME (186RNL) IN RECURRENT GLIOBLASTOMA (RGBM) COMPARED TO AN EXTERNAL CONTROL ARM (ECA)
Authors: Lisa Ensign, Norman LaFrance, Lihong Diao, Kala Tummagunta, Denis Boisvert, Joel Michalek, Andrew Brenner, Melissa Moore, Marc Hedrick, Ruthanna Davi
Journal: Neuro-Oncology (2023)

Abstract BACKGROUND ReSPECT-GBM is a Phase 1/2 study of 186RNL administered by convection enhanced delivery (CED) in patients with rGBM. In Phase I, 15 of 24 patients have achieved a therapeutic absorbed dose defined as &amp;gt; 100 Gy. Based on prior work establishing the comparability of a bevacizumab (Bev) comparator to inform early-phase CED study results, OS of the 15 TAD patients were compared to a Bev ECA. METHODS Recent Bev-treated rGBM clinical trial patients meeting the same eligibility criteria as patients in the ReSPECT-GBM study were identified from the Medidata Enterprise Data Store of aggregated and deidentified patient-level historical clinical trial data. Propensity score (PS) methods were used to select the ECA and align the baseline characteristics of the Bev patients to the ReSPECT TAD cohort. OS estimates were generated using the weighted Kaplan-Meier method and compared with a weighted 2-sample 2-sided log-rank test at α = 0.05 based on a data cut-off of December 2022. RESULTS Baseline characteristics of the ReSPECT TAD and ECA patients were well-aligned after PS modeling. Although not achieving statistical significance due to small sample sizes (median OS 12.2 vs 10.1 months, hazard ratio 0.63, 95% CI: 0.26, 1.52), comparison of OS between the ReSPECT TAD and ECA patients demonstrate consistently longer OS at each 6-month interval: 6 months: 85.1% vs 73.3%, 12 mos: 51.1% vs 30.3%, 18 months: 30.6% vs 25.4%, 24 months: 30.6% vs 3.5%. CONCLUSIONS Single-arm studies can be challenging to interpret. By comparing the ReSPECT-GBM outcomes to an ECA of similar patients with balanced baseline characteristics, we can better appreciate the treatment effect of 186RNL administered via CED. The current results are encouraging, and updated results reflecting current follow-up will be presented at the meeting.
EPCO-43. STING EPIGENETIC SILENCING IN GBM: IMPLICATIONS FOR INFLAMING THE IMMUNE MICROENVIRONMENT AND DESIGNING COMBINATION THERAPIES
Authors: Justin Low, Michelle Bowie, Virginia Wertman, Eric Baker, Avani Mangoli, Emiley Gibson, Rodrigo de La Vega Gomar, Kevin Stevenson, Rebecca Fuller, Janell Hostettler, Michael Brown, Matthew Waitkus, Zachary Reitman, David Ashley
Journal: Neuro-Oncology (2023)

Abstract Primary brain tumors including glioblastoma (GBM) are notoriously resistant to immunotherapy due in part to disrupted innate immunity. The stimulator of interferon genes (STING) pathway is a key component of innate immunity and senses pathogenic cytosolic DNA, stimulating the production of type I interferons (IFN) and pro-inflammatory cytokines. We have recently shown that STING signaling is silenced in the neoplastic compartment of the GBM tumor microenvironment, but remains intact in vascular and immune cells. Methylation analysis of bulk GBM tumor samples revealed a STING promoter region that is highly methylated and strongly correlates inversely with STING RNA expression, suggesting epigenetic control of STING expression. Methylation array analysis of patient specimens demonstrates that such promoter hypermethylation is unique amongst innate immune genes, and STING RNA expression correlates strongly with markers of immune inflammation. STING epigenetic silencing is also present in normal fetal and adult brains, suggesting that STING silencing occurs early in neural development and may provide an immunosuppressive environment conducive to tumorigenesis. Treatment with the blood brain barrier-penetrant DNA methyltransferase inhibitor Decitabine demethylates the STING promoter and activates interferon stimulated genes (ISG). STING knockout experiments and treatment with the DNMT1-selective inhibitor GSK-3685032 suggest that STING expression is necessary but not sufficient for ISG activation. These results suggest that innate immune silencing is a fundamental characteristic of GBM that underlies its intrinsic therapy resistance, yet may also represent a vulnerability that can be exploited by epigenetic therapies to inflame the GBM tumor microenvironment. However, epigenetic therapies that de-represses STING may need to be coupled with DNA damaging agents, immunotherapy, or STING agonists for optimal immune inflammation.
IMMU-58. CHARACTERIZATION OF MYELOID CELL POPULATIONS IN PEDIATRIC HIGH-GRADE BRAIN TUMORS: THE MIMIC PROGRAM
Authors: Tiago Carvalheiro, Joyce Meesters-Ensing, Raoull Hoogendijk, Mariëtte Kranendonk, Kirsten Van Baarsen, Eelco Hoving, Friso Calkoen, Jasper van der Lugt, Stefan Nierkens
Journal: Neuro-Oncology (2023)

Abstract BACKGROUND Pediatric high-grade brain tumors (pHGBT) pose treatment challenges with limited options. Myeloid cells, particularly tumor-associated macrophages (TAMs) in the tumor-microenvironment (TME), exhibit potent immunosuppressive features inhibiting effective anti-tumor T-cell responses. Targeting these cells holds promise to improve outcomes, however the underlying mechanisms of myeloid cell dysfunction remain poorly understood. This study aimed to comprehensively characterize myeloid cell populations in pHGBT and investigate their functional phenotype. METHODS Spectral flow cytometry was performed on tumor tissue (biopsies or resections) and tumor fragments obtained by cavitron ultrasonic surgical aspiration (CUSA) in pHGBT patients (High-grade glioma n=2, Ependymoma n=1, Medulloblastoma n=6, Pilocytic Astrocytoma n=2) enrolled in the MIMIC program. This allowed quantification and comprehensive characterization of myeloid cell populations within the TME. RESULTS The pHGBT TME showed a low abundance of immune cells across different entities, with myeloid cells comprising the predominant proportion. CD49d was used to identify invading cells derived from bone marrow (CD49+) and resident microglia (CD49-). The total TAMs/microglia population was detected in both tumor tissue and CUSA tumor fragments in similar proportions, however resident CD49d- microglia were notably increased in CUSA tumor fragments. Additionally, invading TAMs displayed a mixed "M1" and "M2" polarization phenotype and exhibited higher expression of the chemokine receptor CCR2 and HLA-DR, and of the immune-checkpoint receptors SIRP1A/B, CD33, and TIM3, compared to resident microglia. CONCLUSIONS TAMs play a multifaceted role in pHGBT. The high expression of immune-checkpoint receptors by invading TAMs suggests an immunosuppressive phenotype, potentially facilitating tumor growth, infiltration and (immune)therapy escape. Although, differences between disease entities could not yet be analyzed, disparities were observed in the TME between tumor and CUSA samples, likely related to spatial cellular organization. Understanding TAM dynamics and functional differences between invading and resident subsets, as well as their underlying mechanisms, is crucial for advancing therapeutic efficacy in pHGBT.